The rapid drying of resinous materials via injection of a wet resin solution into a high velocity stream of a hot gas or vapor and expanding same through a nozzle is known in the art and such processes are presently used for the formation of discrete particles of such resinous materials having low moisture content. One example of a drying apparatus and process of the type for which the present invention provides a novel improvement is described by Neblett et al. in U.S. Pat. No. 3,508,339 which issued on Apr. 28, 1970.
In carrying out a rapid drying process for resinous materials, such as polycarbonate resins, it has been found to be generally desirable to employ steam as the hot high velocity vapor medium and to inject the solution of the said resinous material into the high velocity vapor medium at a point downstream of the throat of the nozzle to form a suspension of the resin solution in the hot vapor prior to passing this mixture on to further processing steps to arrive at a segregated solid particulate material having a low moisture content.
It has now been found that in drying solutions of resinous materials, particularly polycarbonate resinous materials via a steam precipitation type process employing an apparatus or processing arrangement similar to that taught in U.S. Pat. No. 3,508,339, the disclosure of which is incorporated herein by reference, or variations of this processing arrangement, it is advantageous to employ a combination of a superheated resin solution and high pressure in order to reduce the quantity of hot high velocity vapor which must be employed, in order to achieve a desired degree of quality in the resultant dry particulate material.
It has also been found that the utilization of a venturi type nozzle wherein the resin solution material is injected into the throat of such nozzle at a discrete angle with relation to the direction of flow of the hot high velocity vapor medium provides for an improved apparatus for carrying out the process of the present invention.